THE AURORA. 23 



light of the zodiacal gleam was applied to that pur- 

 pose, the resulting spectrum would be merely a very 

 faint reproduction of the solar spectrum. 



Recently, however, the zodiacal light has been ana- 

 lyzed by Angstrom, with a result altogether unexpected, 

 and at present almost unintelligible. Its spectrum 

 exhibits a "bright line, and this bright line is the same 

 that is seen in the spectrum of the aurora 'borealis ! 



How are we to understand this most surprising 

 result ? Remembering that the aurora is undoubtedly 

 a terrestrial light, whencesoever it derives its lumi- 

 nosity in other words, that the electric discharges, 

 however excited, really take place in the upper regions 

 of our own atmosphere, while as certainly the zodiacal 

 light is an extra-terrestrial phenomenon the observed 

 phenomenon becomes one of the most perplexing dis- 

 coveries ever made by man. That it will before long 

 be interpreted we have no doubt whatever ; nor do we 

 doubt that the interpretation will involve the explana- 

 tion of a whole series of phenomena which have lately 

 perplexed astronomers. Recalling the association be- 

 tween auroras and terrestrial magnetism, and that 

 between terrestrial magnetism and the solar spots, and 

 remembering further that our physicists have recently 

 detected well-marked signs that the planets in their 

 courses influence the sun's atmosphere and generate 

 his spots in some manner as yet unexplained, we see 

 that the one fact wanting to explain Angstrom's dis- 



